glXUseXFont
generates count display lists, named listBase through listBase+count-1,
each containing a single glBitmap command. The parameters of the glBitmap
command of display list listBase+i are derived from glyph first+i. Bitmap
parameters xorig, yorig, width, and height are computed from font metrics
as descent-1, -lbearing,rbearing-lbearing, and ascent+descent, respectively.
xmove is taken from the glyph's width metric, and ymove is set to zero. Finally,
the glyph's image is converted to the appropriate format for glBitmap.

Using
glXUseXFont may be more efficient than accessing the X font and generating
the display lists explicitly, both because the display lists are created
on the server without requiring a round trip of the glyph data, and because
the server may choose to delay the creation of each bitmap until it is
accessed.

Empty display lists are created for all glyphs that are requested
and are not defined in font. glXUseXFont is ignored if there is no current
GLX context.